class Solution {
public:
    int waysToStep(int n) {
        if (n == 1 || n == 2) return n;
        if (n == 3) return 4;
        vector<int> dp(n + 2);
        dp[1] = 1, dp[2] = 2, dp[3] = 4;
        for (int i = 4; i <= n; i++)
        {
            dp[i] = (dp[i - 3] + (dp[i - 2] + dp[i - 1]) % 1000000007) % 1000000007;
        }
        return dp[n];
    }
};